Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to labels and tags that incorporate a transponder which responds to a radio frequency interrogation signal by identifying an object to which the label is attached, and more particularly to such labels which also include a holographic image or a metallic appearing exterior surface.
2. Description of the Related Art
Radio frequency transponders have been employed to identify objects of various types. For example, identification labels are often placed on items being produced on an assembly line or on airline baggage being sorted at an airport. In another application, such labels are affixed to merchandise in a retail store to detect when a thief attempts to take the merchandise from the premise without paying for it.
It is common to incorporate a radio frequency identification (RFID) transponder circuit into a laminated label which is to be adhered to the object. Many of these transponders employ an integrated circuit which is programmable with information regarding the particular object to which the label is attached. For example, the label for an assembly line can be encoded to identify the particular product model or the features to be incorporated into a specific product being assembled such as the options of a given automobile. For airline baggage, the integrated circuit may store data designating the airline flight number and airport gate, thereby identifying which airplane is to carry a particular luggage item. In a retail store, the label can be encoded at a cash register to indicate that payment has been received for the associated merchandise so that when the merchandise is carried outside, sensors will not sound an alarm.
When the transponder label is placed onto the object, a data encoding device transmits the relevant information to the label via a radio frequency signal. An antenna on the label receives the radio frequency signal which then is detected by the integrated circuit and stored in a memory. Some labels are passive devices in that they are powered by energy from the received radio frequency signal and do not have a battery.
Subsequently, as the object passes down the assembly line or baggage sorting equipment for example, a label reader sends a radio frequency interrogation signal to the label. The label responds to the interrogation signal by reading the previously stored information from memory and transmitting the information via another radio frequency signal. The label reader receives that signal from the label and decodes the transmitted identification information. This enables the specific information about the object to which the label is attached to be obtained by material handling equipment at remote locations from where the label was placed onto the object.
In order for the label to be encoded with information and then be subsequently interrogated, the circuitry on the label must respond to the proper radio frequency used to communicate with the label. However, a problem has been encountered when an RFID label is placed on or near a metal object. The presence of metal in close proximity to the label decreases the inductance and increases the resonant frequency to which the label circuitry is tuned. The resonant frequency often is shifted so far that the label no longer responds to the writing and reading radio frequency signals. One solution to this detuning problem was to place a non-conductive spacer between the label and the metal object. A typical spacer is 6.5 millimeters thick and thus causes the label to stand away from the object far enough so that the metal does not significantly affect the transponder tuning. Although the separation provided by the spacer solves the RF detuning problem, it makes the label considerably thicker and prone to being torn off the object or otherwise damaged during handling. Where the label is to be permanently applied to the object, the relatively bulky size of the label due to the thickness of the spacer often detracts from the appearance of the object.
The present applicants desire to place a reflective holographic image on the label to provide a pleasing appearance. The hologram also makes counterfeiting the label more difficult.
However, heretofore reflective holograms included a metallic layer which reflected light. The metal in that layer interferes with operation of the radio frequency identification transponder by detuning its circuitry from the nominal resonant frequency. Employing the conventional solution would place a relatively thick spacer layer between the RF circuitry and the hologram. However, this produces a label that may be too thick for many applications and which suffers from the disadvantages described previously.
A label for identifying an object includes a radio frequency transponder covered by a non-metallic reflective film, which may form part of a hologram. The radio frequency transponder has an antenna and a transponder circuit attached to an electrically non-conductive layer of material which forms an exterior surface of the label. The hologram forms the other exterior surface of the label with the radio frequency transponder sandwiched between the non-conductive layer and the hologram.
The hologram incorporates the non-metallic reflective film that is adjacent the radio frequency transponder. This film forms a non-metallic reflector of light. A generally transparent image layer contains a transparent holographic image and extends across the non-metallic reflective film. Ambient light passing through the image layer is reflected outward by the film so that an observer can view the holographic image.
Because the reflective film is made of a non-metallic material, its close proximity to the radio frequency transponder does not detune the transponder. This eliminates a need to space the hologram a significant distance from the transponder circuitry, thereby enabling the entire label to have a relatively thin profile.